1. Technical Field
The present invention relates to a vertical cavity surface emitting laser and an atomic oscillator.
2. Related Art
The vertical cavity surface emitting laser (VCSEL) is, for example, used as a light source of the atomic oscillator using coherent population trapping (CPT) which is one of the quantum interference effects.
In the vertical cavity surface emitting laser, a resonator generally has an isotropic structure, and accordingly it is difficult to control a polarization direction of laser light emitted from the resonator. JP-A-2001-189525, for example, discloses a vertical cavity surface emitting laser which includes an insulation layer which is formed to come in contact with an outer surface of a vertical resonator and has an anisotropic stress, and controls a polarization direction of laser light with this anisotropic stress.
However, in the vertical cavity surface emitting laser disclosed in JP-A-2001-189525, the insulation layer is only provided on the side surface of the vertical resonator. Accordingly, in the vertical cavity surface emitting laser disclosed in JP-A-2001-189525, the stress applied to the vertical resonator is not sufficient, and thus the polarization direction of the laser light may not be stabilized.